Sprayed polyurethane (PU) foams have historically used “aromatic polyester polyol” (herein referred to as APP) as a way to improve physical strength and flammability performance. Cost advantages by incorporating APPs are also realized due to a decrease in more expensive raw material usage such as flame retardants and other petroleum based polyols.
With the blowing agent change to primarily HFC-245fa (1,1,1,3,3-pentafluoropropane) for sprayed PU insulation foams, the total amount of APPs in a given “B” side formulation has decreased. Solubility of HFC-245fa in APP's is low and leading to a decrease in APP usage. As HFC-245fa is expensive, water is used as a co-blowing agent to reduce cost. Higher water usage in combination with APPs leads to issues of surface friability in colder application temperatures (<50° F.). Formulators must now replace the APPs with other types of polyols and additives to overcome the obstacles of surface friability and blowing agent solubility.
There exists a significant interest in bio-based spray foams raised by United States Government initiatives which stress the importance of using products with bio-content for all building materials where applicable. In the United States, the Code of Federal Regulations (CFR Title 7 Part 2902) details guidelines for designating bio-based products for federal procurement. In this guideline, the preferred procurement product must have a bio-based content, as measured by ASTM D6866, of at least 7 percent, based on the amount of qualifying bio-based carbon in the product as a percent of the weight (mass) of the total organic carbon in the finished product. The guideline is specifically for spray-in-place plastic foam products designed to provide a sealed thermal barrier for residential or commercial construction applications.